1. Field of the Invention
The present invention relates to a soil sampling apparatus used for geological studies, civil engineering and the like, and a geological observation method using this apparatus.
2. Description of the Related Art
Hitherto, geological sections are observed upon boring the ground in various scientific studies. However, unconsolidated samples obtained by boring are usually disturbed, and the original sedimentary structure of the geological sections can not be observed by the samples.
Trench surveying (Trenching) is also popular as a conventional geological observation method. Trenching is a survey in which a groove, called a trench, is formed in the ground, and geological sections appearing on the inner wall surface of the trench are observed to survey particularly active faults.
Trenching is conducted by heavy civil engineering machinery and produces a large amount of excavated soil in order to make outcrops on trench walls. A stockyard for such large amount of excavated soil must be secured and the soil must be buried in the trench again, requiring a high survey cost.
To survey geographical sections continuously, a wall section under observation must be cut to expose the next observation wall surface. For this reason, the cut observation wall surface cannot be observed or inspected again.
On the other hand, to prevent trench walls from collapsing during observation, trench walls must be maintained at a predetermined gradient. Even in this case, there is always a danger of collapse. In addition, the trench itself can not be excavated easily in soft ground where the ground water level is very high.
On soft ground, to obtain a 3 m wide and 3 m deep outcrop on a trench wall, we need to use a 10 m by 10 m wide land. Therefore, we may loose important geological evidence during an excavation process.
As described above, time-, labor- and cost-intensive works are required in any conventional geological observation method for obtaining subsurface soil layers. In addition, great difficulty is expected in securing sites wide enough to conduct a survey in highly populated areas.